The Collaborative Glaucoma Risks and Outcomes Study (CIGTS-2) is a prospective longitudinal observation study designed to determine the long-term effects of intraocular pressure lowering in preventing or delaying further visual field loss or optic nerve progression due to open angle glaucoma (OAG) in participants recruited into the Collaborative Initial Glaucoma Treatment Study (CIGTS). The Optic Disc Reading Center (ODRC) of CIGTS-2 will support the mission of the study by providing uniform masked interpretation of existing CIGTS baseline and five-year follow-up stereoscopic optic disc photographs. The investigators at the University of Miami are an experienced team, who have been the ODRC for the Ocular Hypertension Treatment Study since 1994. The aims of the CIGTS-2 ODRC are: 1. To establish a protocol for grading optic disc characteristics at baseline and follow-up 2. To evaluate photographic quality 3. To assess development of optic disc progression in a uniform masked manner 4. To re-train and re-certify study photographers 5. To train and certify Primary Readers to grade stereoscopic optic disc photographs for determination of optic disc progression 6. To develop an ODRC infrastructure to receive, log in, track, and archive all stereoscopic optic disc photographs of the CIGTS and CIGTS-2 7. To develop and implement a timely, secure, and reliable data entry and transmittal protocol to transmit databases from the ODRC to the Coordinating Center at the University of Michigan 8. To perform quality assurance procedures at the ODRC to assure reproducible, high quality grading of cup/disc (C/D) ratio and optic disc progression 9. To assist the Coordinating Center to establish a Clinical Assessment Committee protocol to determine if the changes judged by the ODRC are optic disc progression caused by OAG 10. To develop a protocol for the digital archiving of all CIGTS and CIGTS-2 optic disc images and for the construction of a relational database for use by interested researchers in the future 11. To provide the Coordinating Center with optic disc progression rates